There are at least 20 different tick-related illnesses, including the most common Lyme disease. Approximately 300,000 Americans suffer from the ailment each year and, more alarming, researchers are discovering new illnesses linked to the tiny arachnids.

A majority of Lyme disease sufferers who get early treatment fully recover but about 20% of victims experience persistent symptoms including headaches, muscle and joint aches, swollen lymph nodes, rashes, chills and fever.

Since 2004, Lyme disease cases have doubled, according to the report. The Northeast and North Central states are experiencing the biggest proliferation. The group’s findings indicate the spread is due, in part, “to ecological changes taking place in North America since the middle of the 20th century, including habitat and climate changes.”